A motion transmission system in a bicycle comprises a chain extending between toothed wheels associated with the axle of the pedal crank and with the hub of the rear wheel. When there is more than one toothed wheel at at least one of the axle of the pedal cranks and the hub of the rear wheel, and the motion transmission system is therefore provided with a gearshift, a front derailleur and/or a rear derailleur are provided for. In the case of an electronically servo-assisted gearshift, briefly called electronic gearshift herein, each derailleur comprises a chain guide element, also known as cage, movable to move the chain among the toothed wheels in order to change the gear ratio, and an electromechanical actuator to move the chain guide element. The actuator in turn typically comprises a motor, typically an electric motor, coupled with the chain guide element through a linkage such as an articulated parallelogram, a rack system or a worm screw system, as well as a sensor of the position, speed and/or acceleration of the rotor or of any moving part downstream of the rotor, down to the chain guide element itself. It is worthwhile noting that slightly different terminology from that used in this context is also in use.
The toothed wheels associated with the hub of the rear wheel are also known as sprockets, while those associated with the axle of the pedal cranks of the bicycle are also known as crowns or gears.
Control electronics changes the gear ratio automatically, for example based on one or more detected variables, such as the travel speed, the cadence of rotation of the pedal cranks, the torque applied to the pedal cranks, the slope of the travel terrain, the heart rate of the cyclist and similar, and/or the gear ratio is changed based on commands manually input by the cyclist through suitable control members, for example levers and/or buttons.
In gearshifts of a first type, a control device of the front derailleur and a control device of the rear derailleur—or only one of the two in the case of simpler gearshifts—are mounted so as to be easily manoeuvred by the cyclist, usually on the handlebars, close to the handgrips where the brake lever for controlling the brake of the front and rear wheel, respectively, is located. Control devices that allow driving both a derailleur in the two directions and a brake are commonly known as integrated controls. By convention, the control device of the front derailleur and the brake lever of the front wheel are located close to the left handgrip, and the control device of the rear derailleur and the brake lever of the rear wheel are located close to the right handgrip.
In gearshifts of a second type, a control device, again mounted so as to be easily manoeuvred by the cyclist, allows a gearshifting request manual command to be input—which can be to decrease the ratio or to increase the ratio—and the electronic system controls the driving of the front derailleur and/or of the rear derailleur to actuate the requested gearshifting.
The aforementioned components and possibly others are located on-board the bicycle and there are means for communication between them.
U.S. Pat. No. 6,047,230 discloses a bicycle gearshift system comprising a display, an interface to input manual commands, a sensor of the speed of the wheel, a cadence sensor, a gear changer position sensor, a sensor of the tension of a torque transmission member (chain), a clinometer, a sensor of the effort of the cyclist, a heart rate monitor, a drive rate sensor, a controller and a gear changer actuator. The controller generates a control signal based on the detected quantities. The gear changer actuator is coupled to the gear changer and moves it in response to the control signal positioning the torque transmission element with respect to a plurality of toothed wheels.
The system provides for a setting mode of characteristics of the bicycle and of characteristics of the cyclist, as well as various operating modes wherein the decisions on gearshifting are based selectively on constant cadence, constant pedalling force, constant acceleration, constant heart rate, a completely manual mode, a semi-automatic mode wherein manual controls prevail, and a mode based on artificial intelligence and in particular on fuzzy logic the decision parameters of which are the aforementioned detected quantities. The system also inhibits gearshifting if the speed of the wheel is too low or if the tension of the chain is too high.
As far as heart rate is concerned, the system provides that when the heart rate is less than a first threshold, the controller increases the gear ratio and when the heart rate is greater than a second threshold, the controller reduces the gear ratio, wherein preferably the first threshold is less than a target heart rate, that can be stored in the system, by a predetermined quantity, and the second threshold is greater than the target heart rate by a predetermined quantity. The document also notes, without providing any details, the fact that the system adjusts the target heart rate over time to account for warm-up and cool-down intervals.
The invention provides a bicycle electronic system and a method for actuating a bicycle electronic gearshift that provide at least one operating mode that is particularly effective in terms of training.